Cigarette manufacturers increasingly require that the cigarettes with little tendency to ignition meet the legal requirement in the United States that 75% of them extinguish on a support normally consisting of 10 sheets of a particular filter paper type. This percentage of cigarettes that extinguish is measured in the United States through the self-extinguishment test or “SE” for its acronym in English, Self-Extinguishment, ASTM E2187, the only official test currently available.
But in addition, cigarette manufacturers also require the percentage of cigarettes that extinguish during free combustion, that is, without being in contact with anything, to be minimal and, ideally, zero. This is measured using an unofficial test called “FASE” for its acronym in English, Free-Air Self-Extinguishment.
The basis of the measurement of the FASE value is to determine the percentage of cigarettes that burn out completely after lighting them and smoking them for 5 mm (normally in a cigarette smoking machine) and holding them by the filter without touching anything more inside a glass cabinet or similar, where the air circulation is kept as low as possible, to ensure total removal of the smoke from the combustion (this parameter depends on the volume of the glass cabinet, but for the case of a glass cabinet where there is installed a cigarette smoking machine, this flow rate is around 0.5 liter/minute).
There is abundant state of the art on methods to obtain self-extinguishing cigarettes, such as the patent application WO2003/15543. The use of the gum arabic has meant an important contribution in the obtainment of self-extinguishing cigarettes, but it was necessary to improve the filler of the film forming composition replacing the aluminium hydroxide by compounds that increase the percentage of cigarettes that do not extinguish at free combustion.
Calcium carbonate is mentioned in patents as U.S. Pat. No. 4,615,345 but not in the sense of reducing the FASE value comparatively to aluminium hydroxide.
Patent EP1166656 B1 discloses the use of calcium carbonate as the filler with a particle size of 1.3 μm and with different forms. However it is not combined with gum arabic either. Something similar happens in the patent application EP1403432, which discloses the use of calcium carbonate with particle size of diameter less than 1.3 μm.
On the other hand, application US20030178039 mentions gum arabic among possible forming film materials for a composition applicable to papers dispersible in water, as well as calcium carbonate as possible filler in said composition. In addition, both substances are not listed as a specific combination, so there is no incentive for the express combination of both substances. Therefore, the differences between this application and the present invention are: (1) while the new composition object of this application is directed to the so-called “cigarette paper”, the application US20030178039 is directed only to the plug wrap and tipping paper; (2) the object of the present invention is the extinction of the cigarettes, while the object the application US20030178039 is to promote the dispersibility in water of the filter papers and mouthpiece.
With the paper obtained according to the present invention lowering the FASE value for a given SE value comparatively to aluminium hydroxide is achieved, as it will be shown below.